RFR: 8333893: Optimization for StringBuilder append boolean & null [v4]

[Shaojin Wen]

On Tue, 11 Jun 2024 11:35:28 GMT, Shaojin Wen <duke at openjdk.org> wrote:

>> After PR https://github.com/openjdk/jdk/pull/16245, C2 optimizes stores into primitive arrays by combining values ​​into larger stores.
>> 
>> This PR rewrites the code of appendNull and append(boolean) methods so that these two methods can be optimized by C2.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   revert

In the AbstractStringBuilder#appendNull method, is it possible to not check the bounds based on the information from ensureCapacityInternal?


class AbstractStringBuilder {
    private AbstractStringBuilder appendNull() {
        int count = this.count;
        ensureCapacityInternal(count + 4);
        byte[] val = this.value;
        if (isLatin1()) {
            val[count    ] = 'n';
            val[count + 1] = 'u';
            val[count + 2] = 'l';
            val[count + 3] = 'l';
        } else {
            StringUTF16.putCharsAt(val, count, 'n', 'u', 'l', 'l');
        }
        this.count = count + 4;
        return this;
    }
}

-------------

PR Comment: https://git.openjdk.org/jdk/pull/19626#issuecomment-2163035274